Defect engineering in a semiconductor nanowire-based device has aroused intensive attention due to its fascinating properties and the potential applications in nanoelectronics. Here in this work, in order to investigate the effect of oxygen defects on the electrical transport properties in a SnO ₂-nanowire-based device under normal environment, we synthesize an individual SnO ₂nanowire, by a thermal chemical vapor deposition method and further construct a two-terminal Au/SnO ₂nanowire/Au device by using optical lithography. The electrical transport properties of a single SnO ₂nanowire device are measured under the condition of air and vacuum after hydrogen reduction. It is found that the transport performances in air are unusually different from those in vacuum. Strikingly, the reduction of electric current through the device and the increment of contact barrier of the Au/SnO ₂interface in air can be observed with the I-Vscan times increasing. While in vacuum, the current increases and a change from Schottky contact to ohmic contact at the interface between Au and SnO ₂can be obtained by performing more scans. Our results demonstrate that the oxygen vacancy concentrations caused by the oxygen atom adsorption and desorption on the surface of nanowires play the key role in the transport properties. Furthermore, we calculate the relevant electronic properties, including energy band structure, density of states, as well as I-Vcharacters and transmission spectrum at the interface of Au/SnO ₂within the framework of density functional theory. We find that the bandgap of SnO ₂nanowires decreases with oxygen vacancy concentration increasing. Also, the existence of oxygen defects enlarges the electron transmission at the interface of Au/SnO ₂and enhances electrical transport. Therefore, our results provide a new strategy for designing the integrated nano-functional SnO ₂-based devices.